State of Vermont

Be Alert for Blue-Green Algae in Lakes and Ponds

For Immediate Release: August 8, 2003

Contact: Linda Dorey
Vermont Department of Health
802-863-7312

BURLINGTON—Hot, dry, calm weather conditions promote the growth of blue-green algae, which are commonly seen in Lake Champlain and other lakes and ponds throughout the state. The blue-green algae appears as a heavy greenish-blue scum on the water or shoreline.

In some cases, these algae blooms can release toxins such as microcystin or anatoxin.

People should avoid swimming in areas where there is visible green or blue-green scum collected on the surface of the water. Ingestion (drinking) of algae that are producing toxin can result in symptoms including nausea, vomiting, and diarrhea. Skin exposure can result in irritation or allergic reactions. Children should especially be kept from entering scummy water since they are more likely to ingest the water than adults.

In the hot summer of 1999, several dogs died after ingesting large quantities of blue-green algae in Lake Champlain.

Dogs are at risk if they eat the algae or drink the water in an area where a toxic algae bloom is taking place. They may also ingest the algae by licking their fur after they have been in water that is thick with algae.

Not all blue-green algae blooms produce toxin. However there is no way to tell just by looking at it. Most other algae lake plants do not produce any toxin.

When blue-green algae bloom, they look thick like pea soup or blue or green paint on the water. They are mostly blue-green, although they can also be brown or purple. When blue-green algae washes up on shore, it can form a thick mat or foam on the beach.

Generally, lots of wind, cooler weather, rainfall, and cloudy days will lead to the collapse of an algae bloom. Some blooms die off after a few days or weeks, while others persist for a few months.